1. Field of the Invention
The present invention relates to a method of and an apparatus for damping the vibration of a building caused by an earthquake and strong wind pressure.
2. Description of the Related Art
In high-rise buildings, the period of vibration caused by an earthquake or strong wind pressure is long, and swaying motion still continues for a while even after the earthquake or the strong wind has substantially subsided, imparting a sense of uneasiness or fear to the occupants of the building. In recent years, therefore, vibration damping apparatuses, which are adapted to operate with a period coinciding with the period of natural vibration of the building as a whole, have come to be installed in highest stories of high rise buildings where the amplitude of vibration is the largest.
As such a vibration damping apparatus, a vibration damping apparatus has been developed which is constructed such that roller members are interposed between a pair of upper and lower clamping members whose opposing surfaces are formed with circular arcuate cross sections, respectively, the lower clamping member being fixed on a highest story of a high-rise building, and a weight being mounted on the upper clamping member, as disclosed in Japanese Patent Application No. 161678/1992. According to this vibration damping apparatus, when the building is subjected to vibration due to an earthquake or the like, the weight vibrates in the same direction with a phase lag of a predetermined period, and the upper clamping member supporting the weight sways over the circular arcuate surface of the lower clamping member via the roller members, thereby making it possible to suppress the vibration of the building by absorbing the vibrational energy of the building.
However, since the above-described vibration damping apparatus is capable of operating only passively in synchronism with the primary natural period of the building, although the effect of suppressing the vibration in the primary mode is large, the vibration damping apparatus is difficult to respond to quick vibration in a higher mode. Moreover, since the apparatus is operated only after the building has swayed, there is a drawback in that it is difficult to suppress large vibrations in an early period. In addition, when the vibration of the building becomes large, there is the risk that the upper clamping member with the weight mounted thereon may become dislocated from the lower clamping member, rendering the apparatus itself inoperable and possibly causing damage to the apparatus and the building.
For this reason, so-called active vibration-damping apparatuses have been developed in which an actuator is connected between the weight of such a passive vibration damping apparatus and a building, the magnitude of the vibration of the building is detected by a sensor, and the operation of the actuator is controlled in correspondence with the detected amount thereof. However, since, when the vibration of the building has become large, as described above, and exceeded the capacity of the apparatus, the actuator is stopped to ensure the safety of the apparatus, there is a drawback in that the overall vibration damping apparatus becomes integrated with the building, and fails to demonstrate the vibration-damping effect.